Optical subassembly enclosure

ABSTRACT

A housing for optoelectronic devices provides EMI shielding and axial strain suppression for optical fibers coupled to optoelectronic devices retained within the housing. The housing includes an internal septum for EMI shielding and a grounding scheme including relief features of the conductive housing coupled to internal grounding strips. The housing provides a first exemplary engaging/locking feature including an orthogonal tongue and a groove that receives the tongue, and a second exemplary engaging/locking feature that includes a groove having an intermittently varying cross-sectional area and that retains a gasket of constant cross-sectional area. Arms extend from the housing and retain an optical fiber that is secured to the arm by an adhesive such that axial strain is not exerted at the point of optical coupling and a high optical coupling efficiency is maintained. In an exemplary embodiment, the housing includes an opening through a bottom surface, the opening bounded by beveled edges to aid in blind alignment of the housing over components formed on a mounting surface. The bottom of the housing includes a recessed portion that retains a gasket. The recessed portion receives a gasket of constant thickness and includes a gap of varying thickness that provides for sufficient compression throughout the gasket and a tight, EMI-shielding seal formed between the housing and the mounting surface.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application claims the benefit of U.S. Application SerialNo. 60/254,420, entitled “Optical Subassembly Enclosure”, filed on Dec.8, 2000, the contents of which are hereby incorporated by reference.

DIVISIONAL STATUS

[0002] This application is a divisional application of co-pending U.S.application Ser. No. 10/011,685, filed Dec. 4, 2001.

FIELD OF THE INVENTION

[0003] The present invention relates, most generally, to optoelectronictelecommunications systems. More particularly, the present inventionrelates to an enclosure for housing optical subassemblies and associatedcomponents.

BACKGROUND OF THE INVENTION

[0004] Optoelectronic devices such as vertical cavity surface emittinglasers (VCSELs) and other lasers, photodiodes and other photodetectors,have become widely used in the telecommunications and other industries.In optoelectronic devices, an electrical signal is converted to anoptical signal that travels along a transmission medium such as anoptical fiber and is then typically converted back to an electricalsignal. A high optical coupling efficiency ensures good optoelectronicconnections. The electrical-to-optical optoelectronic connections aretypically made in optical subassemblies (OSAs) such as TOSAs(transmission OSAs) and ROSAs (receiving OSAs). The optoelectronicdevices and the connection of the optical transmission media to theoptoelectronic devices are typically delicate, and therefore an OSAhaving stable mechanical support as well as a high quality opticalconnection helps ensure a high optical coupling efficiency.

[0005] The optoelectronic devices commonly used in today'stelecommunication industry typically operate at high frequencies such as2.5-10 GBPS (gigabits; per second) and higher. Therefore, when an OSAand the associated high frequency components are joined to a customerboard or other mother board which contains low frequency components, itis desirable to suppress EMI (electromagnetic interference) noise fromadversely affecting other portions of the module circuitry such ascircuitry operating at other frequencies. Optoelectronic devices, andthe various OSAs which contain them, are typically included in anenclosure or housing that contains various other electronic componentsand is joined to the customer board or other mother board. The housingmay be configured to be mounted over further electronic componentsmounted on the customer board.

SUMMARY OF THE INVENTION

[0006] The present invention provides a housing for housingoptoelectronic components such as TOSAs and ROSAs, printed circuitboards, and the like. The housing is suitable for various optoelectronicdevices. In one exemplary embodiment, the housing is a multiple-piecehousing which, according to one exemplary embodiment of the invention,includes an internal septum that suppresses high frequency noise such asEMI and RFI from traveling between the chambers of the housing.

[0007] According to another embodiment of the invention, the housingincludes a peripheral engaging feature including a groove, a gasket, anda tongue that is received within the groove and compresses the gasket.The peripheral engaging feature may be used to suppress high frequencynoise such as EMI and RFI.

[0008] According to another exemplary embodiment, the present inventionprovides a channel having a cross-sectional area that variesintermittently along the longitudinal direction. The corrugated channelretains a gasket and allows for an improved and continuously tight sealto be formed between the components which combine to form themultiple-piece housing.

[0009] According to another exemplary embodiment, the housing of thepresent invention includes an opening through its bottom surface. Thehousing is mounted on a mounting surface such that components formed onthe mounting surface are nested within the housing. The bottom of thehousing includes a recessed portion having a bowed surface and a gasketreceived within the recessed portion. The gasket combines with the bowedrecessed portion to form a tight seal between the housing and themounting surface. The tight seal is capable of suppressing EMI and RFInoise.

[0010] According to another exemplary embodiment, the housing of thepresent invention includes internal grounding leads which contact relieffeatures of the conductive housing and direct internal errant signals tothe internal grounding strips and eventually the intended ground path.

[0011] According to another exemplary embodiment, the present inventionincludes an opaque housing having an internal portion and an externalportion and a bottom surface having an opening therethrough. The openingthrough the bottom is bounded by beveled edges that aid in the blindalignment of the housing over components formed on the mounting surface.

[0012] According to yet another exemplary embodiment, the housingfurther includes means for alleviating axial strain on optical fibersextending from the housing and optically coupled to optoelectronicdevices within the housing. The present invention provides arms thatextend from the housing and retain optical fibers. The optical fiber isjoined to the arm by means of an adhesive. Axial strain at the opticalconnection is alleviated because the optical fiber is affixed to thehousing at a point external to the optical connection, and therefore nostrain is exerted at the optical coupling point and the optical couplingefficiency is not compromised. A pocket formed in the arm of theenclosure contains the adhesive which bonds the optical fiber to theenclosure arm.

BRIEF DESCRIPTION OF THE DRAWINGS

[0013] The present invention is best understood from the followingdetailed description, when read in conjunction with the accompanyingdrawings. It is emphasized that, according to common practice, thevarious features of the drawings are not to scale. On the contrary, thedimensions of the various features are arbitrarily expanded or reducedfor clarity and to emphasize features of the present invention. Likenumerals refer to like feature throughout the specification anddrawings. Included are the following figures:

[0014]FIG. 1 is a perspective view showing an exemplary lower portion ofthe optoelectronic housing of the present invention;

[0015]FIG. 2 is a perspective view showing an exemplary upper portion ofthe optoelectronic housing of the present invention;

[0016]FIG. 3 is a perspective view of the lower portion of theoptoelectronic housing including internal components and showing OSAscoupled to optical fibers;

[0017]FIG. 4 is a cross-sectional view showing an optical fiber securedto a pocket formed in an arm portion of the optoelectronic housing ofthe present invention;

[0018]FIG. 5 is a cross-sectional view showing an optical fiber securedto a complete arm of the optoelectronic housing of the presentinvention;

[0019]FIG. 6 is a cut-away perspective view showing internal sections ofan assembled optoelectronic housing of the present invention;

[0020]FIG. 7 is a cross-sectional view of an exemplary peripheralengaging/locking feature of the present invention;

[0021]FIG. 7A is an expanded cross-sectional view of the peripheralengaging/locking feature shown in FIG. 7;

[0022]FIG. 8 is a cross-sectional view showing another exemplaryembodiment of a peripheral engaging/locking feature of the presentinvention;

[0023]FIG. 9 is a perspective view showing exemplary grounding strips ofan exemplary grounding scheme of the present invention;

[0024]FIG. 10 is a side view of elements of the exemplary groundingscheme of the present invention;

[0025]FIG. 11 is a perspective view of a corrugated channel of anexemplary engaging feature of the present invention;

[0026]FIG. 12 is an expanded perspective view of the corrugated channelof the engaging feature of the present invention;

[0027]FIG. 13A is a plan view of an exemplary corrugated channel of thepresent invention;

[0028]FIG. 13B is a cross-sectional view of a wide portion of thecorrugated channel of the present invention;

[0029]FIG. 13C is another exemplary cross-sectional view of a narrowportion of the corrugated channel of the present invention;

[0030]FIG. 14 is a cross-sectional view showing a gasket within anengagement feature including the corrugated channel of the presentinvention;

[0031]FIG. 15 is a side view of an exemplary optoelectronic housing ofthe present invention;

[0032]FIG. 16 is a plan view of the bottom of an exemplaryoptoelectronic housing of the present invention;

[0033]FIG. 17 is an expanded side view of the optoelectronic housing ofthe present invention showing a recessed portion on the bottom of thehousing;

[0034]FIG. 18 is a perspective view showing the bottom of an exemplaryoptoelectronic housing including a sealing gasket; and

[0035]FIG. 19 is a perspective view of the bottom of an exemplaryoptoelectronic housing according to the present invention including anopening surrounded by beveled edges.

DETAILED DESCRIPTION OF THE INVENTION

[0036] The present invention provides an enclosure for housingoptoelectronic components. The enclosure may alternatively be referredto as a housing and may be produced by machining, or it may be die cast.

[0037] According to an exemplary embodiment, the housing may be atwo-piece enclosure including a lower portion such as shown in FIG. 1and an upper portion such as shown in FIG. 2. The housing is designed tobe mounted on a customer board or other mother board. The housingincludes various optoelectronic devices retained internally. MultipleOSAs may be included within the housing. According to an exemplaryembodiment, the housing may include both a TOSA and ROSA. The TOSA andROSA may advantageously be mounted upon a printed circuit board (PCB)sized to fit securely within the housing. In one embodiment, the TOSAand ROSA may be shielded from another to minimize cross-talk. The OSAsmay included VCSELs (vertical cavity surface emitting lasers) or otherlasers configured to emit light generally along a direction parallel tothe printed circuit board and the external board on which the housing ismounted. The OSAs include the optical connection between theoptoelectronic device and an optical fiber that may extend out of thehousing through an arm. In an exemplary embodiment, the arms extend fromthe sides of the housing and generally parallel to the external mountingboard on which the housing is mounted. The internal printed circuitboard may include electronic components mounted on each of its upper andlower surfaces. The bottom of the housing may include an opening throughwhich internal components are coupled to traces and other electroniccomponents included on the customer board on which the housing ismounted. The opening in the bottom of the housing may also enable thehousing to be mounted on the mounting board and over electroniccomponents formed on the mounting surface such that the electroniccomponents are covered and essentially internal to the housing.Components formed on the bottom of the internal PCB may be positionedwithin the opening. In another exemplary embodiment, an internal printedcircuit board may not be used and the internal components may be securedwithin the housing using other media.

[0038] The upper and lower portions that combine to form the housing mayeach be formed of aluminum, zinc or conventional alloys such as aluminumalloys, zinc alloys and other suitable alloys or conductive materials.For example, Zamac No. 3, which is a zinc alloy, or aluminum 383, may beused. The housing is sized and shaped in accordance with the componentswhich it will house and in accordance with its application. Generallyspeaking, when OSAs including high frequency devices are used, theassociated high frequency components used to power and monitor the highfrequency optoelectronic devices, are located in close-proximity to thehigh frequency optoelectronic devices in order to minimize the length ofthe connection and maintain a controlled impedance. These high frequencycomponents are shielded, for example from other components to preventhigh frequency noise such as EM waves from degrading the performance ofthe other components. The low frequency components located within andexternal to the housing must be shielded from noise such as EMI and RFInoise. Furthermore, errant signals within the housing may be grounded toavoid degrading the performance of the various components in and nearthe housing. The pieces that combine to form the housing may be tightlysealed and the housing is joined to the mounting board with anadvantageously tight seal to suppress EM waves from propagating throughthe interface formed between the portions that combine to form thehousing or between the housing and the mounting board.

[0039] According to one exemplary embodiment, the present inventionprovides an internal septum that suppresses noise from escaping theinternal chamber in which it is produced and also suppresses externalnoise from entering the chamber. According to another embodiment of thisinvention, the suppression of high frequency noise and cross-talk isachieved by a novel engaging/locking mechanism disposed peripherallyaround the housing. According to still another aspect of the presentinvention, a corrugated channel having a varying cross-sectional area isused to retain a gasket and enables a tight seal to be formed betweenopposed sealing surfaces of the respective portions that combine to formthe multiple-piece housing. According to yet another aspect of thepresent invention, a grounding scheme is provided to direct errantsignals through the conductive housing and to an internal ground.Another aspect of this exemplary embodiment is a tight seal formedbetween the bottom of the housing and the mounting surface. This tightseal prevents the loss of EM waves from components formed on themounting surface, that extend within an opening through the bottom ofthe housing. According to still another aspect of this embodiment, axialstrain upon the optical fiber is relieved and a high optical couplingefficiency is achieved. This embodiment also provides for the blindalignment of the opaque housing over optical components due to bevelededges formed around an aperture extending through the bottom of thehousing.

[0040] Now turning to the figures, FIG. 1 is a perspective view showingan exemplary lower portion of an exemplary optoelectronic housing of thepresent invention. According to the exemplary embodiment, lower portion5 combines with upper portion 45 shown in FIG. 2 to form an exemplarytwo-piece enclosure or housing of the present invention. According toother exemplary embodiments, more than two portions may be combined toform the housing. Lower portion 5 includes bottom 7 and sidewalls 9.Sidewalls 9 define interior 11. Interior 11 includes bottom surface 13in one area and aperture 15 extends through bottom 7 of lower portion 5in another area. Lower portion 5 also includes ribs 17 and 19. Withinsidewall 9 and extending peripherally about lower portion 5, groove 21extends downward from upper surface 23 of sidewall 9. Each of bottom 7and bottom surface 13 are generally flat. Internal ribs 17 and 19provide a base upon which an integral printed circuit board or othercomponent-containing member may rest. According to an exemplaryembodiment, a printed circuit board (not shown) extends over aperture 15where components such as connectors which may be formed on the undersideof the printed circuit board, may be coupled to external components.

[0041] According to one exemplary embodiment, a pair of OSAs may bemounted within the housing such as on a printed circuit board atapproximately locations 37 and 39. In an exemplary embodiment in whichthe two OSAs are a TOSA and ROSA, partition 41 is provided to minimizecross-talk between the transmit and receive optical subassemblies.According to other exemplary embodiments, partition 41 may not be neededor partitions of other suitable shapes may be used. According to anexemplary embodiment, the housing may include one or more arms thatextend from the sides of the housing and are capable of retaining anoptical fiber having a fiber launch direction being generally parallelto bottom surface 13 and also generally parallel to the mounting surfaceon which bottom 7 is advantageously mounted. In this manner, the opticalfibers are retained for coupling to an optoelectronic device configuredto transmit or receive light along a direction generally orthogonal tobottom surface 13 and bottom 7. In an exemplary embodiment, the arms aregenerally cylindrical and shaped to guide an optical fiber, internallyconnected to an OSA mounted in interior 11, out of the housing. In anexemplary embodiment, each arm is formed of sections of more than oneportion that combine to form the multiple-piece housing of the presentinvention. As such, FIG. 1 shows a duality of lower arm portions 25L.Each of lower arm portions 25L combines with a corresponding upperportion to form a generally cylindrical arm that encircles and axiallyretains an optical fiber in an exemplary embodiment. Each exemplary armincludes proximate portion 27 and distal portion 29. Proximate portionincludes width 28, which is greater than width 30 of distal portion 29.Lower arm portion 25L includes recess 31 and axial opening 33, whichextends concentrically through the arms, in one exemplary embodiment.Other, non-cylindrical arm configurations may be used alternatively.Moreover, according to other exemplary embodiments, opening 33 mayextend non-concentrically through the arms.

[0042]FIG. 2 is a perspective view showing upper portion 45 of anexemplary housing of the present invention. Upper portion 45 may bejoined to lower portion 5 shown in FIG. 1, to form an exemplary housing.Upper portion 45 includes sidewalls 47 and top 57. Sidewalls 47 includetongue 49 which extends below surface 48 which may be a sealing surfacejoined to a surface of the lower housing portion when the upper andlower portions are engaged, in an exemplary embodiment. Upper portion 45includes ribs 51 and septum 53. Upper arm portions 25U include recesses55. According to an exemplary embodiment, when upper and lower portionsare joined to form the optical housing of the present invention, septum53 may provide EMI shielding and rib 51 may contact a grounding strip todirect errant EM waves to ground. Tongue 49 may be received within acorresponding groove formed within the lower portion, such as groove 21shown in FIG. 1.

[0043] Axial Strain Suppression

[0044] One aspect of the present invention is the suppression of axialstrain that may be externally exerted upon an optical fiber. FIG. 3shows OSAs 65 which each include an internal optoelectronic device andsecure a respective optical fiber 61. Optical fiber 61 is terminallyencased within ferrule 63 which extends into OSA 65. Ferrule 63 andoptical fiber 61 may include co-planar ends or their respective ends maybe in close proximity to one another. OSAs 65 may include variousconfigurations for coupling an optical fiber to an optoelectronic deviceaccording to the various exemplary embodiments. In one exemplaryembodiment, OSAs 65 may include a barrel shaped receptacle for retainingferrule 63 and optical fiber 61. Within OSA 65, optical fiber 61 issecured and optically coupled to an optoelectronic device includedwithin OSA 65. The end of optical fiber 61 may contact theoptoelectronic device within OSA 65 or it may be spaced from theoptoelectronic device within OSA 65. According to either of theforegoing exemplary embodiments, the optical coupling arrangement may bea delicate and precise arrangement and the correct positioning of theoptical plane of the end of the optical fiber 61 is helpful to ensurehigh optical coupling efficiency. Ferrule 63 may optionally be affixedto OSA 65 by various conventional means.

[0045] Optical fiber 61 is tightly encased within a jacket that extendsalong the length of the fiber. The jacket provides mechanical supportand protects the fiber. If axial strain is asserted upon optical fiber61 in an outward direction, the quality of the mechanical connection tothe optoelectronic device within OSA 65 will be compromised and theoptical coupling efficiency will be diminished. Optical fiber 61 mayextend for several hundred meters and, as such, there is a considerablelikelihood that outward axial strain may be exerted upon optical fiber61. The fiber launch direction is generally parallel to the mountingsurface upon which lower portion 5 is mounted, increasing the likelihoodof axial strain being exerted. Optical fiber 61 extends throughexemplary axial opening 33 formed within the arm. Recess 31 formedinternal to lower arm portion 25L, partially engulfs optical fiber 61.Lower arm portion 25L is an integral projection of lower portion 5 andis a continuous portion thereof. The arm formed when lower arm portion25L is joined to upper arm portion 25U, is configured to retain portionsof ferrule 63 within wider proximate portion 27 of the arm and opticalfiber 61 in the narrower distal portion 29 of the arm. Recess or pocket31 is formed within distal portion 29.

[0046] Strain relief is achieved by including an adhesive, such as aconventional epoxy, in recess 31, then placing optical fiber 61 intoposition. The epoxy may be a conventional UV-curable epoxy or othersuitable epoxies. According to one exemplary embodiment, Locktite 352may be used. Other suitable adhesives may be used alternatively.According to one exemplary embodiment, a drop of adhesive is introducedinto recess 31, then optical fiber 61 may be aligned into position bymeans of conical alignment member 67 or by placing upper arm portion 25Ushown in FIG. 2, into position over corresponding lower arm portion 25Lof lower portion 5 to form the housing. A volume of adhesive may beadded such that the adhesive at least partially (and maybe completely)surrounds optical fiber 61 when optical fiber 61 is in position withinthe completed arm formed of lower arm portion 25L and upper arm portion25U. Optical fiber 61 is therefore directly secured to the arm at apoint past ferrule 63, relative to the housing.

[0047]FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 3and shows optical fiber 61 secured into an exemplary position. Referringto FIG. 4, adhesive 77 is added within pocket or recess 31 of lower armportion 25L of the housing and then optical fiber 31 is placed intoposition as above. The adhesive may then be cured or otherwisesolidified. According to this exemplary embodiment, upper arm portion25U may be secured over lower arm portion 25L without adding any furtheradhesive.

[0048] According to another exemplary embodiment such as shown in FIG.5, adhesive 77 may circumferentially surround optical fiber 61 and mayfurther extend within a corresponding recess 55 formed in top portion 45and opposite recess 31 formed in lower arm portion 25L. Although theshape of the recess shown in the cross-sectional representation of thecombination of lower arm portion 25L and upper arm portion 25U isessentially rectangular, such is intended to be exemplary only and therecesses may take on other configurations in other exemplaryembodiments. After the arrangement such as shown in FIGS. 4 and 5 isformed, the adhesive may be treated or allowed to solidify to secureoptical fiber 61 into position. In the exemplary embodiment in whichadhesive 77 is an epoxy, the epoxy may be cured by UV-curing,temperature curing, or other curing means to secure optical fiber 61into position. The curing process may take place before or after upperarm portion 25U is placed into position as shown in FIG. 5.

[0049] Now returning to FIG. 3, it can be seen that any axial strainexerted upon optical fiber 61 is not transferred to the point whereoptical fiber 61 is coupled to the optoelectronic device secured withinOSA 65. In this manner, the optical coupling efficiency may be increasedby not allowing the strain to propagate through to the ferrule 63.

[0050] Recesses 31 and 55 may be formed by machining, or they may beformed as part of the die cast. The generally cylindrical shape of thearms and the generally axial positioning of optical fiber 61 within thearms formed of upper and lower arm portions 25U and 25L, respectively,is intended to be exemplary only. The arms are generally configured toretain an optical fiber therein, the optical fiber generally extendingsubstantially parallel to the top and bottom surfaces of the housing.Other arm shapes may be used in other exemplary embodiments. FIG. 3 alsoshows printed circuit board (PCB) 69 positioned within internal portion11 of lower portion 5. PCB 69 includes top surface 71 and extends overbottom surface 13 and aperture 15 such as shown in FIG. 1. Variousexemplary components 75 are formed on top surface 71 of PCB 69. Dashedline 73 generally represents the location along which exemplary septum53 of upper portion 45 (shown in FIG. 2) will be positioned.

[0051] Internal Septum for Noise Suppression

[0052] According to another exemplary embodiment of the presentinvention, an internal septum and gasket combination shields internalhigh frequencies from escaping from the localized compartment in whichthe active high frequency generating components are included. Anexemplary internal septum is shown as septum 53 shown in FIG. 2. Septum53 is integrally formed as part of upper portion 45 and extendssubstantially vertically from top 57 of upper portion 45. When upperportion 45 is engaged with lower portion 5 shown in FIG. 1 to form anexemplary housing of the present invention, septum 53 extends laterallyacross the enclosure, just forward of aperture 15 shown in FIG. 1 andfunctions as an internal septum, separating a first section of theinternal chamber from a second section of the internal chamber. Septum53 may alternatively be described as an internal wall that forms aseptum in combination with a gasket, as will be shown in FIG. 6.

[0053] Referring again to FIG. 3, it can be seen that various components75 are formed on printed circuit board 69 which is seated within lowerportion 5 and extends from front to back according to the arbitraryspatial designation assigned in FIG. 3. Septum 53, shown in FIG. 2,generally extends along dashed line 73 shown in FIG. 3 when top portion45 shown in FIG. 2 is secured in position over lower portion 5 shown inFIG. 1. According to an exemplary embodiment, components on printedcircuit board 69 that are forward of dashed line 73, such as OSAs 65,may be high frequency components. Meanwhile, components such ascomponents 75 that are rearward of dashed line 73 may operate at other,lower frequencies. Beneath these lower frequency components, additionallow speed components may be included on the underside and beneathprinted circuit board 69. Similarly, additional low frequency componentsmay be included external to the housing and may be coupled to internalcomponents such as through aperture 15 shown in FIG. 1. Septum 53 istherefore positioned to prevent the escape of high frequency EMI noisefrom the internal chamber portion in which the high frequency componentsare housed, such as forward of dashed line 73. According to otherexemplary embodiments, septum 53 may separate two substantially internalchambers from one another, such as a TOSA-containing chamber from aROSA-containing chamber. In an exemplary embodiment, the TOSA mayinclude a VCSEL or other optical source and the ROSA may include aphotodiode or other exemplary photodetectors. Septum 53 may be generallyformed to shield components of one chamber of the housing from othercomponents, and vice versa, regardless of the operating frequencies andfunctions of the components.

[0054] Still referring to FIG. 3, when the upper and lower portions areengaged with exemplary printed circuit board 69 in place, septum 53 issized so that it nearly forms an interface with upper surface 71 ofprinted circuit board 69. The gap, which would otherwise form betweenthe lower surface of septum 53 and upper surface 71 of printed circuitboard 10 is filled by a resilient member such as gasket 79 shown in FIG.6.

[0055]FIG. 6 is a cutaway view taken longitudinally through an exemplaryassembled housing including upper portion 45 joined to lower portion 5.Printed circuit board 69 includes upper surface 71 and bottom surface89. Components 91 formed on bottom surface 89 extend within aperture 15of lower portion 5. Septum 53 extends downward from top section 45.Together with gasket 79, septum 53 forms a shield that shields EMI fromthe left side of the septum 53/gasket 79 configuration, from componentson the right side thereof, and vice-versa. Septum 53 extends completelyacross the enclosure and the gap that otherwise would exist betweenbottom 83 of septum 53 and surface 71 of PCB 69 is filled by gasket 79.Gasket 79 is formed of an insulating material such as a conventionalresilient elastomer material or other suitable materials. Lower surface85 of gasket 79 is formed of this insulating elastomer. The othersurfaces of gasket 79 are formed of conductive material 87, which may begold plated brass according to an exemplary embodiment. Other suitableconductive materials may be used alternatively. Upper surface 81 ofgasket 79 covered with conductive material 87, contacts bottom 83 ofseptum 53. Insulating lower surface 85 of gasket 79 forms an interfacewith upper surface 71 to prevent electrical shorting between conductivetraces formed on upper surface 71. Gasket 79 contains conductivematerial 87 on its sides to form a continuous and impenetrable signalbarrier in conjunction with septum 53 which it contacts. In an exemplaryembodiment, gasket 79 may include a D-shaped or semicircularcross-section with the flat section oriented downward and contactingupper surface 71. In this manner, a metallic signal barrier may beformed continuously from upper surface 71 to the top of upper portion 45by means of the septum 53/gasket 79 combination. According to thisarrangement, noise such as EMI produced by the active componentcircuitry is reduced or suppressed from leaving the localized area ofthe chamber portion in which it is generated. Such EMI noise may bedirected along septum 53 and/or conductive material 87 to a ground path,which may be internal to said housing.

[0056] The positioning and configuration of the septum is intended to beexemplary only. Various other arrangements may be used to shield highfrequency components from other components and the septum may be shapedand positioned differently depending on the location of the variouscomponents in order to optimally suppress transmission of the energygenerated by the active circuitry, or to preclude external interferencefrom affecting the module generators. According to one exemplaryembodiment, the septum/gasket configuration may be formed to divide achamber portion containing a ROSA from another chamber portioncontaining a TOSA.

[0057] Engaging/Locking Feature for Noise Suppression

[0058] According to another aspect of the present invention, anengaging/locking mechanism extends peripherally around the housing toprovide a tight seal between the portions of the housing and suppressnoise produced by high frequency signals such as internally generatedEMI radiation and RFI noise produced external to the housing. Aspects ofthe engaging/locking mechanism are described in conjunction with FIGS.1, 2, 8, 8A and 9. FIG. 1 shows exemplary groove 21 extendingperipherally around lower portion 5 and FIG. 2 shows correspondingtongue 49 extending peripherally around upper portion 45. Tongue 49 isreceived within groove 21 when the upper and lower portions are engaged.Groove 21 has a generally rectangular cross-section and mayalternatively be referred to as a channel. In one exemplary embodiment,a gasket is included within groove 21 and beneath tongue 49 when theupper and lower portions are engaged.

[0059]FIG. 7 shows a representative cross-section of an exemplaryengaging/locking mechanism of the present invention. Tongue 49 extendsdown from upper portion 45 and is received within groove 21 formedwithin sidewall 9 of lower portion 5. Tongue 49 is generally orthogonaland includes a series of 900 bends. Tongue 49 extends orthogonally fromupper surface 48, which essentially forms a ledge. As discussedpreviously, both tongue 49 and groove 21 may each extend peripherallyaround the housing to mate with each other. Other arrangements may beused alternatively. Gasket 101 is placed within groove 21 and may be acontinuous member sized to extend completely within groove 21. Gasket101 may be a conventional gasket chosen to have appropriate shieldingeffectiveness to shield high frequencies. According to an exemplaryembodiment, gasket 101 may be formed of an elastomer, for example, itmay be an EMI gasket including silver plated copper impregnated in asilicon elastomer, but other suitable materials may be usedalternatively. According to various exemplary embodiments, gasket 101may be an elastomeric gasket either impregnated, coated or otherwiseencased in an electrically conductive material. Groove 21 extendsdownward in sidewall 9 and is bounded by sides 95 and 97 which are ofdifferent height. Sides 95 and 97 include top surfaces 105 and 106,respectively. Outer side 97 includes upper surface 106 that contactsupper surface 48 of top portion 45 when the upper and lower portions ofthe housing are engaged. In an exemplary embodiment, upper surface orledge 48 forms a conterminous boundary with top surface 106. Theinterface formed between upper portion 45 and lower surface 5, includes90′ bends.

[0060]FIG. 7A is an expanded cross-sectional view of a portion of FIG.7. In the exemplary embodiment, tongue 49 includes ledge 107 which restson top surface 105 of inner side 95 of sidewall 9. According to otherexemplary embodiments, groove 21, sides 95 and 97 and tongue 49 may haveother suitable cross-sectional shapes to enable groove 21 to retaingasket 101 and receive tongue 49. For example, sides 95 and 97 may bethe same height. According to the various embodiments, groove 21 is adeep groove capable of retaining gasket 101 and receiving tongue 49.

[0061]FIG. 8 is a cross-sectional view of another arrangement of anexemplary engaging/locking feature and shows the arrangement prior tothe engagement of upper portion 45 and lower portion 5, and thereforeprior to the compression of gasket 101. Sides 108 and 109 of sidewall 9are the same height in the exemplary embodiment shown in FIG. 9. In thisexemplary embodiment, each of inner and outer surfaces 113 of upperportion 45 forms a substantially conterminous boundary withcorresponding top surfaces 110 and 111 of sides 108 and 109,respectively. When the portions are engaged and such a boundary isformed, tongue 49 compresses gasket 101 within groove 21. Compressedgasket 101 therefore contacts each of tongue 49 and the inner surfacesof groove 21.

[0062] Referring to the embodiments shown in FIGS. 7, 7A and 8, whenupper portion 45 is engaged with lower portion 5 such that the matingsurfaces are in contact, orthogonal tongue 49 extends into groove 21 andcompresses gasket 101. Gasket 101 may have a circular cross-section whenin a relaxed state but other gasket configurations may be used in otherembodiments. The combination of top portion 45 including tongue 49,gasket 101 and lower portion 5, provides a shield against EMI radiationescaping from internal portions of the enclosure to external portions ofthe enclosure. In this embodiment, EMI radiation cannot easily escapethrough the orthogonal interface formed between the upper and lowerportions in the exemplary embodiments. Even if the interface formedbetween 110 and 113, and 111 and 113 of FIG. 9 does not include aperfect seal, tongue 49 helps prevent EMI radiation from escapingbecause there is no crevice available to act as a slot antenna. Theinterface formed between the upper and lower portions is not a simpleplanar interface. The corners formed by orthogonal tongue 49 can cancelout EMI waves as they attempt to propagate through the interface formedby the engaging/locking feature. Since any high frequency signal orother forms of noise such as EMI radiation typically travels along theinterface formed between the upper and lower portions, the 900 bendsprovided by the engaging/locking feature of the present invention, causethe electromagnetic waves to induce charge on the surface of theconductive housing that provides an electromagnetic field whichpartially cancels the incident electromagnetic wave. Whenelectromagnetic waves are forced to traverse corrugation such as the 900bends produced, the electromagnetic waves are attenuated or completelydestroyed and do not successfully traverse the interface.

[0063] Grounding Scheme

[0064] According to another exemplary embodiment, the present inventionprovides a grounding scheme. The grounding scheme provides for groundingthe conductive housing through the intended grounding path. Groundingleads are formed along either or both of the top and bottom surfaces ofa printed circuit board such as printed circuit board 69 shown in FIG.3. According to an exemplary embodiment, each of the top and bottomsurface of the printed circuit board contains a set of grounding leadsthat are formed along the side edges and which generally extend fromfront to back according to the arbitrary spatial designations assignedin FIGS. 3 and 9. FIG. 9 shows printed circuit board 69 which includes aset of grounding leads 117 formed on top surface 71. Grounding leads 117may be formed using conventional methods and may formed of lead or tinor other suitable conventional materials. Each grounding lead 117 mayextend along or in close proximity to edge 119 and may also extend fromthe front to the back of printed circuit board 69. In the exemplaryembodiment shown, each of grounding leads 117 forms a straight strip.This is exemplary only and according to other exemplary embodiments, thegrounding leads may take on different shapes and be placed in differentlocations. In an exemplary embodiment, further grounding leads will alsobe formed on the bottom surface of printed circuit board 69. Thegrounding leads formed on the bottom surface of printed circuit board 69may take on various configurations and in an exemplary embodiment theymay be formed opposite the grounding leads formed on upper surface 71.

[0065]FIG. 10 is a cross-sectional view showing grounding lead 117formed on top surface 71 and grounding lead 121 formed oppositegrounding lead 117 on bottom surface 91. The corresponding upper andlower grounding leads are electrically coupled through via 123. Via 123also provides coupling to internal ground plate 125. According to otherexemplary embodiments, printed circuit board 69 may include multiplegrounding plates such as the singular internal grounding plate 125illustrated in FIG. 10. According to another exemplary embodiment inwhich upper and lower grounding leads 117 and 121 respectively, are notformed opposite each other, multiple vias may be used to separatelycouple the respective grounding strips to the internal ground plate.

[0066] The housing may be formed of a conductive material and isdesigned so that when the upper and lower portions of the housing areengaged by clamping or other fastening means, each of the upper andlower portions of the housing are grounded to the grounding leads suchas grounding leads 117 and 121 of printed circuit board 69. Morespecifically, each of the upper and lower portions of the housinginclude relief features that mechanically contact either the upper orlower grounding lead when the portions of the housing are engaged. Forexample, as shown in FIG. 1, ribs 17 and 19 of lower portion 5 maymechanically contact lower grounding lead 121 of printed circuit board69 when the printed circuit board is inserted within the housing and theportions of the housing are engaged. Similarly, ribs 51 of upper portion45 shown in FIG. 2 may mechanically contact upper grounding lead 117shown in FIG. 9. The various ribs for providing mechanical contact asshown in FIGS. 1 and 2 are intended to be exemplary only. Various otherrelief features may be used to ensure that, when the upper and lowerportions of the housing are engaged, mechanical contact is made betweenthe grounding leads and the upper and lower portions of the housing. Theinternal ground plate 125 integral to printed circuit board 69 istherefore electrically coupled or grounded to the grounding leads formedon the top and bottom of the printed circuit board as well as todirectly to the upper and lower portions of the conductive housing. Inthis manner, errant signals travel through the conductive housing to theinternal ground plate which directs errant signals along an intendedgrounding path which may be external to the housing.

[0067] Corrugated Channel for Improving Sealing and EMI ShieldingPerformance

[0068] According to another exemplary embodiment, the present inventionprovides a channel having a cross-sectional area that varies along thelongitudinal direction of the channel. The corrugated channel isconfigured to receive a gasket and to provide for a uniform seal betweenthe facing sealing surfaces of the multiple portions that combine toform the housing of the present invention. The cross-sectional area ofthe corrugated channel may vary intermittently along regular orirregular intervals. The varying cross-sectional area may include aplurality of minimum cross-sectional area portions for tightly securinga gasket having a constant cross-sectional area chosen to fit snuglywithin the minimum cross-sectional area portions of the channel. Byretaining a gasket having a constant cross-sectional area within theirregular channel, the gasket in this embodiment achieves addedcompression only at “pinch points” (points of minimum cross-sectionalarea), and therefore an increase in contact pressure can be used tosecure the upper portion of the housing without fear of bunching thegasket and forming gaps between the facing sealing surfaces at locationsbetween fastening points, as a result. According to the embodiment inwhich an upper portion and lower portion combine to form a two-piecehousing, the lower portion may include the corrugated channel andgasket. According to other exemplary embodiments, the corrugated channelmay be included in the upper portion of the housing or it may beincluded in each of the upper and lower portions. According to othermultiple-piece housing embodiments, any or all of the portions mayinclude the corrugated channel and gasket.

[0069]FIGS. 11 and 12 are perspective views showing irregular channel131 formed within sidewall 9 of lower portion 5. Irregular channel 131extends downward from upper sealing surface 133 and within sidewall 9.Lower portion 5 will be joined to an associated upper portion (notshown) to form the multiple-piece housing of this embodiment of thepresent invention. When joined, upper sealing surface 133 willadvantageously contact a facing sealing surface of the upper portion.

[0070] When a gasket (not shown) having a substantially constantcross-sectional area is placed within irregular channel 131 formedwithin upper sealing surface 133 of lower portion 5, and a cover in theform of an upper portion is positioned into place over lower portion 5,the varying cross-sectional area of corrugated channel 131 allows for anincreased pressure to be applied to join the portions together to formthe housing. Regularly spaced fastening means such as screws, may beused to join the portions together to form the housing after a gasket isplaced within irregular channel 131. Irregular channel 131 and thegasket allow for a tight and uniform seal to be formed between theopposed sealing surfaces. The design of the irregular channel of thepresent invention provides for maximum compression of the gasket only atthe pinch points, and therefore prevents the gasket seated within theirregular channel from bunching and preventing facing sealing surfacesof the upper and lower portions from forming a conterminous boundary atsuch bunching locations between the fastening members. According tosealing methods of prior art, a space could result between the intendedsealing surfaces and of the upper and lower portions due to springing orflexing of the housing in locations between the fastening members. Thepresent arrangement prevents springing or flexing of the housingportions. The openings produced by springing or flexing of the housingportions of the prior art, reduce the housing shielding effectiveness byallowing for the transmission of EMI or RFI noise into or out of thehousing. Screws, clamps or other fastening means may be used to join theupper and lower portions at the fastening points.

[0071] Exemplary rounded projections 135 extend into irregular channel131 to vary the cross-sectional area of irregular channel 131 along thelongitudinal direction. Although shown as rounded projections 135 thatextend into irregular channel 131 in each of FIGS. 11 and 12, variousother configurations for producing a channel having an intermittentlyvarying cross-sectional area along its longitudinal direction may beused. Furthermore, the indentations that project into irregular channel131 need not be formed at opposed locations and across from each otherwithin the channel. In an exemplary embodiment, irregular channel 131includes regularly repeating minimal cross-sectional area portions. FIG.13A is a top view of the irregular channel. Corrugated or irregularchannel 131 includes narrow sections 141 and wide sections 143.Irregular channel 131 extends downward from upper sealing surface 133.Gasket 139 is included within irregular channel 131. Gasket 139 includesa generally constant cross-sectional area indicated by diameter 145according to the embodiment in which gasket 139 is round. Across-sectional view taken along line 1313-1313 of wide section 143 isshown in FIG. 13B.

[0072] In FIG. 13B it can be seen that gasket 139 is not tightly seatedwithin wide section 143 of irregular channel 131. Wide section 143 is sodesignated because width 144 at the top of wide section 143 and depth153 of wide section 143 provide a greater cross-sectional area than thecorresponding dimensions in narrow section 141. Gasket 139 is in anon-fully compressed state in wide section 143. In an exemplaryembodiment, gasket 139 may be minimally compressed when an opposed,generally flat sealing surface mates with upper sealing surface 133.Gasket 139 includes an essentially constant cross-sectional area anddiameter 145. Gasket 139 may be formed of conventional compressiblematerials such as commercially available elastomers; and may be eitherimpregnated, coated, or otherwise encased in an electrically conductivematerial. Gasket 139 may be a solid gasket such as shown in theexemplary embodiments shown in FIGS. 14B and 13C, or it may include ahollow core.

[0073]FIG. 13C is a cross-sectional view taken along line 13C-13C ofnarrow section 141 shown in FIG. 14A. Narrow section 141 is produced atlocations in which opposed rounded projections 135 are formed inirregular channel 131. Narrow section 141 includes width 142 along uppersealing surface 133 and -depth 155. Width 142 and depth 155 of narrowsection 141 are chosen in this embodiment, so that the cross-sectionalarea of narrow section 141 is less than that of wide section 143. FIG.13C shows that gasket 139 is essentially tightly sealed withincorrugated channel 131 at narrow section 141. In this embodiment, narrowsection 141 may be considered a pinch point for gasket 139 andrepresents the minimal cross-sectional area of the corrugated channel131 and the maximum compression points of gasket 139, when an opposedgenerally flat sealing surface is brought into contact with uppersealing surface 133. FIG. 14 is a cross-sectional view showing narrowsection 141 of irregular channel 131. Gasket 139 is compressed at thepinch point represented by narrow section 141. Upper portion 45 includessealing surface 159 which forms an interface with upper sealing surface133 and also contacts gasket 139. Depth 155 and diameter 145 of gasket139 are substantially similar.

[0074] According to the exemplary embodiment in which the intermittentlyvarying cross-sectional area of irregular channel 131 does so in regularintervals, distance 149 (FIG. 13A) between regularly spaced narrowsections 141, may be considered the pitch and may be the wavelength ofthe maximum desired shielding frequency, divided by ten, in an exemplaryembodiment. According to an exemplary embodiment, the irregular channelfeature of the present invention may be used in conjunction with thetongue/groove engaging/locking feature of the present invention asdescribed in conjunction with FIGS. 7, 7A and 8. In other words, in thisembodiment, irregular channel 131 may include pinch points of reducedcross-sectional area and be designed to accommodate a gasket ofsubstantially constant cross-sectional area and a tongue from theopposed mating surface to aid in compressing the gasket at pinch points.According to this exemplary embodiment, irregular channel 131 may extenddown from sides of unequal height such as shown in FIG. 7.

[0075] EMI Suppression Within Mounted Housing

[0076]FIG. 15 is a side view of housing 200 including bottom portion 201and upper portion 202. Housing 200 includes arm 225 formed of portionsof each of bottom portion 201 and upper portion 202. Lower portion 201includes sidewalls 209 and bottom 207. Bottom 207 is adapted to bemounted on or over a mounting surface such as a customer board or othermother board. Bottom 207 includes a recessed portion being recessedabove lowermost surface 221 of bottom 207. Housing 200 includesconnector sites 206 at which connectors such as machine screws or otherfasteners may be used to join housing 200 to the mounting surface. Asshown in the side view, a gap is created between upper surface 210 ofthe recessed portion and lowermost surface 221 of bottom 207. Gap 216formed at connector sites 206 is greater than gap 214 formed atintermediate locations 204 between the connector sites.

[0077]FIG. 16 is a plan view showing bottom 207 of lower portion 201.Bottom 207 includes centrally located base portion 212 that includeslowermost surface 221. In an exemplary embodiment, lowermost surface 221is essentially planar. In the exemplary embodiment shown, recessedportion 226 extends peripherally around bottom 207. and also betweenbase portion 212 and opening 222. Recessed portion 226 may take onvarious other shapes and is shaped to accommodate a gasket therein.Recessed portion 226 includes upper surface 210. Recessed portion 226includes openings 230 which may be connector openings in the exemplaryembodiment. Connector openings 230 are located at connector sites 206.Locations 204 are located between connector sites 206. In an exemplaryembodiment, connector opening 230 may be an opening through which afastener such as a machine screw may be inserted to secure bottomsurface 207 of lower portion 201 onto a mounting surface. As shown inthe side view of FIG. 15, lowermost surface 221 of base portion 212extends below upper surface 210 of recessed portion 226. The gap betweenupper surface 210 and lowermost surface 221 is greater at connectorsites 206 than at locations such as location 204 between connector sites206. This is achieved because upper surface 210 of recessed portion 226is bowed downward as shown in FIG. 15. In the exemplary embodiment shownin FIG. 16, the cross-hatched area may represent bowed area 218.According to other exemplary embodiments, the contour of recessedportion 226 may be varied and bowed section 218 may be a larger orsmaller portion of recessed portion 226 in order to provide that the gapformed between upper surface 210 and lowermost surface 221 is greater atconnector sites 206 than at locations 204 between connector sites 206.In this manner, when a gasket of constant thickness is placed withinrecessed portion 226, a greater compressive force will desirably beachieved within the gasket at locations 204 than at connector sites 206.According to another exemplary embodiment, the compressive force withinthe gasket is constant throughout. Without the variation in the gap, andaccording to the prior art, the gasket may not be in compressionthroughout and the seal formed at locations 204 between connector points206, may not be a tight seal enabling propagation of EMI and RFI waves.According to other exemplary embodiments, any of various numbers ofconnectors and connector sites may be used, as an alternative to thefour exemplary sites shown in FIG. 16.

[0078]FIG. 17 is an expanded side view of housing 200 and shows gap 216at connector site 206 and gap 214 at location 204 between connectorsites 206. Lowermost surface 221 is essentially planar in the exemplaryembodiment. Upper surface 210 of recessed portion 226 is not planar andtherefore gap 214 is less than gap 216. In an exemplary embodiment, gap216 may be {fraction (25/1000)} inch and gap 214 may be {fraction(18-20/1000)} inch. This provides a gap variation of 5{fraction(7/1000)} inch throughout recessed portion 226. Such are intended to beexemplary only and other gap thicknesses and variations may be used inother exemplary embodiments.

[0079]FIG. 18 is a perspective view showing bottom 207 of housing 200.FIG. 18 shows gasket 232 seated within recessed portion 226. Gasket 232includes thickness 234 which may be a constant thickness according to aexemplary embodiment. Thickness 234 is chosen so that gasket 234 extendsbelow lowermost surface 221 of base portion 212 when seated withinrecessed portion 226. In this manner, lower surface 236 will form aninterface with the mounting surface on which housing 200 is mounted.When machine screws or other fastening means are provided withinconnector openings 230 to secure housing 200 to a mounting surface, thecompression of gasket 232 will desirably be greater at locations 204than at connector sites 206 due to the bowed upper surface of therecessed portion 226. According to an exemplary embodiment, thickness234 may be {fraction (32/1000)} inch and the gasket 232 may undergo acompression of {fraction (7/1000)} inch at connector sites 206 and acompression of 12{fraction (13/1000)} inch at locations 204 betweenconnector sites 206. Such thicknesses and degrees of compression areexemplary only and gasket 234 may be formed of various thicknesses andmay achieve different degrees of compression at connector sites 206 andlocations 204.

[0080] The configurations shown in FIGS. 16-18 are intended to beexemplary only and the recessed portion may take on other shapes withrespect to the base section above which it is recessed. For example,base section 212 may take on various shapes and positions other thancentrally positioned base portion 212. Generally described, the recessedportion extends above the base section and includes a lower surface thatis higher than the surface of the base section and is spaced above thebase section by a first distance at connector sites and by a seconddistance at other sites, the second distance being less than the firstdistance to desirably ensure at least as much gasket compression betweenthe connector sites as at the connector sites.

[0081] Self Alignment Feature

[0082]FIG. 19 is another perspective view showing bottom 207 of lowerportion 201 of housing 200. Opening 222 extends through bottom 207 andis bounded by a beveled edge 224. According to an exemplary embodiment,housing 200 is formed of an opaque material. The opaque materials may bevarious conductive materials and their alloys as described above. Whenhousing 200 is mounted on a mounting surface, housing 200 may bepositioned so that components on the mounting surface which are to bereceived and nested within opening 222 are not damaged by bottom 207 ofhousing 200 when attempting to align the housing into position usingmanual or other tactile alignment methods. In an exemplary embodiment,housing 200 may house components that convert and condition anoptical/electrical signal that is presented to the housing through aconnector interface such as through components on the mounting surfacewhich are received within opening 222. Since housing 200 is opaque, ablind alignment of the housing, in particular opening 222 over thecomponents, is carried out. Without being able to see opening 222relative to the components which it may desirably surround, beveled edge224 provides for aligning housing 200 over the components throughtactile feedback or feel for the mating connector. Beveled edge 224assists in aligning housing 200 over the components without damaging thecomponents. When the housing is mounted on the mounting surface andpositioned over the components, the components are tightly nested andextend within opening 222.

[0083] The preceding merely illustrates the principles of the invention.It will thus be appreciated that those skilled in the art will be ableto devise various arrangements which, although not explicitly describedor shown herein, embody the principles of the invention and are includedwithin its scope and spirit. Furthermore, all examples and conditionallanguage recited herein are principally intended expressly to be onlyfor pedagogical purposes and to aid in understanding the principles ofthe invention and the concepts contributed by the inventors tofurthering the art, and are to be construed as being without limitationto such specifically recited examples and conditions. Moreover, allstatements herein reciting principles, aspects, and embodiments of theinvention, as well as specific examples thereof, are intended toencompass both structural and the functional equivalents thereof.Additionally, it is intended that such equivalents include bothcurrently known equivalents and equivalents developed in the future,i.e., any elements developed that perform the same function, regardlessof structure. The scope of the present invention, therefore, is notintended to be limited to the exemplary embodiments shown and describedherein. Rather, the scope and spirit of the present invention isembodied by the appended claims.

What is claimed is:
 1. A sealing feature for a multiple-piece housingfor optoelectronic devices, said sealing feature including a channelhaving an intermittently varying cross-sectional area and capable ofreceiving therein a gasket having a substantially constantcross-sectional area.
 2. The sealing feature as in claim 1, in whichsaid channel includes a plurality of minimum cross-sectional areaportions capable of tightly securing said gasket.
 3. The sealing featureas in claim 2, wherein said channel is formed within a first sealingsurface formed in a first piece of said multiple-piece housing and asecond piece of said multiple-piece housing includes a second sealingsurface and, when said gasket is disposed within said channel and saidfirst piece and said second piece are joined to form said multiple-piecehousing, said first sealing surface and said second sealing surface forma substantially conterminous boundary and said gasket includes maximumcompression points substantially only at each of said plurality ofminimum cross-sectional area portions.
 4. The sealing feature as inclaim 3, further comprising fastening means securing said first piece tosaid second piece.
 5. The sealing feature as in claim 2, wherein saidchannel is formed within a first sealing surface formed in a first pieceof said multiple-piece housing and a second piece of said multiple-piecehousing includes a second sealing surface including a tongue extendingtherefrom, and, when said gasket is disposed within said channel andsaid first piece and said second piece are joined to form saidmultiple-piece housing, said first sealing surface and said secondsealing surface form a substantially conterminous boundary, said tongueis received within said channel and compresses said gasket, and saidgasket includes maximum compression points only at each of saidplurality of minimum cross-sectional area portions.
 6. The sealingfeature as in claim 1, in which said cross-sectional area variesregularly.
 7. A multiple piece housing for optoelectronic devicescomprising a first piece including a first sealing surface andcontacting a second sealing surface of a second piece, and a corrugatedchannel formed within said first sealing surface and retaining a gaskethaving a substantially constant cross-sectional area, said gasketcontacting said second surface and ridged portions of said corrugatedchannel.